This disclosure relates to a semiconductor structure, and more particularly to a semiconductor structure including conventional silicon-based integrated circuits combined with photonic components based on optically active semiconductor materials. This disclosure also provides a method of fabricating such a semiconductor structure.
In order to obtain high speed signal transmissions and processing, it is desirable to use light instead of electric currents for the transmission of signals. However, photonic components realizing optical storage, imaging, modulation, optical sensing and light sources are difficult to integrate with state of the art CMOS or BiCMOS electronic circuits. This is because silicon-based technology or silicon has an indirect band gap, which is less suitable for realizing light sources. Rather, semiconductor materials having a direct band gap as, for example, III-V semiconductor compounds exhibit optical gain. The integration of so-called compound semiconductors with silicon is difficult because of a large lattice mismatch between the semiconductors.
U.S. 2007/0170417 A1 proposes the integration of photonic circuits on silicon. By bonding a wafer of III-V material as an active region to silicon and removing the substrate, lasers, amplifiers, modulators and other devices are processed using standard photolithographic techniques on the silicon substrate. According to U.S. 2007/0170417 A1, the compound materials are directly bonded onto the silicon wafer having a pre-structured photonic circuit. Any active electronic components, like for example transistors, are eventually fabricated in the silicon domain.
It is still desirable to improve integrated optics, in particular silicon photonics.